This illustration released by the Centers for Disease Control and Prevention depicts a 3-D computer-generated image of a group of carbapenem-resistant Enterobacteriaceae bacteria. (Centers for Disease Control and Prevention/Associated Press)

Rising infections caused by a type of bacteria resistant to multiple antibiotics is causing longer hospitalizations and may mean a higher risk of death for children in the United States, according to a new study.

The study, published this week in the Journal of the Pediatric Infectious Diseases Society, found that 3 out of 5 children admitted to hospitals already had an antibiotic-resistant infection — suggesting these infections are spreading more often in the community.

“Antibiotic resistance increasingly threatens our ability to treat our children's infections,” said Sharon Meropol, the study’s lead author and an assistant professor of pediatrics, epidemiology and biostatistics at Case Western Reserve University School of Medicine.

In analyzing data from 48 children's hospitals across the country between 2007 and 2015, the researchers focused on about 107,000 children younger than 18 who contracted infections caused primarily by Enterobacteriaceae, a family of bacteria that includes dangerous strains resistant to most antibiotics. The results showed that the proportion of multidrug-resistant Enterobacteriaceaeinfections rose sharply, from 0.2 percent to 1.5 percent, over the eight years.

The study also found that children with these drug-resistant infections had 20 percent longer hospital stays than pediatric patients with more treatable infections. Cases involving the bacteria may pose a higher risk of mortality, the researchers noted, though the study did not find a statistically significant association.

Previous research on antibiotic-resistant infections showed that factors such as young age, gender, certain medical conditions and even geography can increase a child's risk. Although weak or underdeveloped immune systems partly explain younger children's vulnerability, the association between resistant infections and older ages is more difficult to explain, Meropol said.

In part, fewer broad-spectrum antibiotics suitable for children can mean more antibiotic-resistant infections go untreated, according to Meropol. Yet the frequency of antibiotic use in the United States is a decided factor in the rising incidence of infections, she said.

According to a report by the Centers for Disease Control and Prevention, health-care providers prescribed 842 antibiotic courses per 1,000 people in the United States in 2011. “About 30 percent of antibiotic use is either inappropriate or unnecessary in the U.S.," said Theoklis Zaoutis, professor of pediatrics at the Children's Hospital of Philadelphia, who was not part of the pediatric study.

Of course, antibiotics are not confined to people. The CDC has highlighted their use for agricultural purposes, such as enhancing growth and treating diseases in food-producing animals, and the danger that the surviving bacteria in farm settings develop resistance, multiply and spread.

“Paying attention to our environment, water and soil is very important when addressing antibiotic-resistant bacteria,” said Helen Boucher, director of the Infectious Diseases Fellowship Program and a professor of medicine at the Tufts Medical Center.

Correction: An earlier version of this post incorrectly suggested that all Enterobacteriaceae strains are resistant to antibiotics.